MAG3 SPECT: a rapid procedure to evaluate the renal parenchyma

Renal parenchymal (cortical) scintigraphy (planar or SPECT) is indicated for the diagnosis and follow-up of focal functional disorders, such as acute pyelonephritis, and for accurate quantitation of split renal function, especially in cases of atypical location of the kidney(s). This static imaging procedure is currently performed 3-5 hr after the injection of a cortical fixation agent, 99mTc-DMSA or 99mTc-GH, and requires effective immobilization of the patient for 30 min.

In five healthy adult volunteers and five children with various clinical indications, SPECT renal parenchymal scintigraphy was performed with a three-detector camera in 1-min per revolution sequential intervals for a total acquisition time of 4 min, beginning immediately after an intravenous injection of a graduated dose of 20 mCi (minimum 2 mCi) of the dynamic renal agent 99mTc-MAG3.

Tomograms of the renal parenchyma reconstructed in three projections and volume-rendered reprojection of the SPECT-volume data indicated normal or abnormal renal parenchyma. Comparisons were made with planar MAG3 and SPECT-GH and favored MAG3-SPECT. However, comparisons with DMSA indicated certain disadvantages of MAG3 SPECT. For most organs, the radiation dose estimates from 20 mCi MAG3 were lower than those from DMSA (6 mCi) or GH (20 mCi). Simultaneous injection of MAG3 and a diuretic (2-40 mg furosemide) resulted in lower than usually reported radiation dose estimates for the urinary bladder (target organ) and the gonads, and allowed subsequent evaluation of the drainage system.

MAG3 SPECT is feasible, clinically useful and may be offered as a rapid (4 min) renal parenchymal imaging procedure, or it may precede planar dynamic (dluretic) MAG3 scintigraphy.